1. Field of the Invention
The present invention relates to the technical field of digital signal processing and, more particularly, to an electrocardiogram signal compression and de-compression system.
2. Description of Related Art
Because the generation of electrocardiogram (ECG) requires continuously recording electrocardiogram signals, typical medical instruments usually do not have enough memory for processing the signals. Taking the existent multi-lead-tapeless ECG Holter system as an example, it uses semiconductor memory as storage media. The semiconductor memory has to store a system program and three ECG signal recordings each for continuous 24 hours. The storage of such data requires a great amount of memory, resulting in high cost for many medical instruments.
Due to the great amount of data and long recording time for ECG, there are lots of ECG signal compressing methods proposed for reducing the cost. As a result, current medical instruments generally use a data compressing method to reduce the cost. By compressing the ECG signals, the memory space can be saved and thus the ECG data can be conveniently added into a central database, so as to perform analysis and comparison data for therapy subsequently. Because the amount of the compressed data is small, it is able to transmit the data in real time via a wired or wireless channel, whereby the prior heart rate monitoring system can be integrated into a portable device to facilitate in monitoring the heart rate of a patient at any time.
FIG. 1 is a schematic diagram illustrating the ECG signals, wherein the important information in the ECG signals focuses on P, Q, R, S and T waveforms, including their positions, shapes, sizes, etc. The P waveform stands for the effect of an atrium (of the heart), in which the left atrium receives the blood full of oxygen from the lung and the right atrium receives the blood without oxygen from the hole body, and this effect continues for about 90 ms. The next part of ECG is QRS-complex waveform, which stands for the effect of a chamber (of the heart), in which the left chamber sends the blood full of oxygen to the whole body and the right chamber sends the blood without oxygen to the lung, and this effect continues for about 80 ms. During the period of time that the QRS-complex waveform appears, the atrium of the heart gradually resumes and prepares to repeat another cycle. During the T waveform, the chamber of the heart also gradually resumes and prepares to repeat another cycle. The time between two adjacent QRS-complex waveforms or R waveforms is a reciprocal of the heartbeat frequency. These data should be reserved to the best no matter what compressing method is used.
The prior art only considers compression of the ECG signals and thus devotes to increasing the compression ratio (CR) of the technique. However, with the advance of the technology, no matter for the flash memory, the dynamic random access memory or the hard disk, the storage capacity has been greatly increased, so that the compression ratio is no longer the major target for ECG compression. In turn, the depression of distortion can provide excellent reconstructed signals for allowing the doctors to make a most correct decision. Therefore, it is desirable to provide an improved electrocardiogram signal compression and de-compression system to mitigate and/or obviate the aforementioned problems.